Arenesulfonyl Halides: A Universal Class of Functional Initiators for Metal-Catalyzed “Living” Radical Polymerization of Styrene(s), Methacrylates, and Acrylates

Abstract

The complex Cu(I)Cl/4,4‘-dinonyl-2,2‘-bipyridine (bpy9) catalyzes via a redox process the homogeneous “living” radical polymerization of styrene(s), methacrylates, and acrylates initiated with a variety of functional phenylsulfonyl chlorides. Polymers with narrow molecular weight distribution and molecular weights close to the theoretical ones are obtained from these three classes of monomers. Kinetics of propagation and initiation were performed with selected substituted phenylsulfonyl chlorides and with their monoadducts to monomer. Polymerizations follow first-order kinetics internally in monomer and externally in Cu(I)Cl while initiation is first order internally in initiator and in Cu(I)Cl concentrations. A catalyst concentration dependence of the optimum bpy9/Cu(I)Cl ratio which yields the largest rate constant of polymerization was observed. The apparent rate constants of propagation corrected for catalyst concentration are in the order: methacrylates > styrene > acrylates. This inversion from the classic dependence of the corresponding absolute rate constants (acrylates > methacrylates > styrene) was shown to be determined by a different steady-state concentration of propagating radicals which is in dynamic equilibrium with an extremely large excess of the corresponding dormant C−Cl species. The formation and the concentration of the radical species is determined by the C−Cl bond strength of the dormant species. Apparent rate constants of initiation corrected for catalyst concentration are in the order: styrene > methacrylates > acrylates. Within experimental error, initiation efficiency is 100% and the apparent rate constants of initiation are 4 (for styrene and methacrylates) and 3 or 2 (for acrylates) orders of magnitude higher than those of propagation. The absence of conjugation between the sulfonyl radical and its phenyl group generates a small effect of the phenyl group substituent on the rate constant of initiation. These results demonstrate that arenesulfonyl chlorides are the first class of universal functional initiators for the metal-catalyzed “living” radical polymerization of styrene(s), methacrylates, and acrylates. This discovery provides numerous fundamental and technological opportunities in the field of controlled radical polymerization and copolymerization, of well-defined functional polymers and copolymers with complex architecture, and of self-organized supramolecular systems based on them.